Volkswagen AG further “improved” its defeat device software long after the German automaker came into the crosshairs of Californian regulator CARB, research of the investigative co-op of Germany’s Süddeutsche Zeitung and the NDR and WDR TV stations shows. “Unbeknownst to U.S. regulators, Volkswagen developers augmented the illegal defeat device with a software update,” NDR says. According to the researchers, this improvement happened around the end of 2014, or beginning of 2015, with the aim of a more efficient cheat.

According to the report, the previous version of the cheater code was fraught with false positives; it sometimes signaled that the car was under supervision on the dyno while in fact it was on the road with nobody watching. This would have led to the exhaust being treated, at least occasionally. “This caused the car to erroneously switch into clean test mode, and it led to increased wear on the particulate filter,” the report continues. To fix that, the new software version also monitored movements of the steering wheel, the report says. “This reliably detected that the car was on the road, and the exhaust gas treatment could be reduced.”

By November 2014, particulate filters of 6,700 Volkswagen diesel cars had malfunctioned, and without a fix, Volkswagen expected some 50,000 additional cases, the report says. End of December 2014, approximately 500.000 vehicles were invited to a service action. 280.000 vehicles received the improved update.

In the first half of 2014, CARB had requested information from Volkswagen to explain abnormally high emission readings during normal use of VW diesel cars. Volkswagen offered a voluntary update. “Apart from the exhaust gas issue. the update apparently also attempted to solve the problems with the particle filter,” the report says. CARB checked again in May of 2015, and noticed that movements of the steering wheel influenced the car’s emissions. “By measuring the steering angle, the improved software possibly was the decisive factor that enabled CARB to identify the illegal defeat device,” the report concludes. Volkswagen did not want to comment.

When Ferdinand Piech took over as CEO of Volkswagen in 1993, one of his first orders of business was to adapt Toyota’s continuous improvement philosophy, called “Kaizen.” The program was teutonified into “Kontinuierlicher Verbesserungs Prozess,” or KVP. 20 years later, KVP was so rigorously implemented that even the cheating was improved, well after it had come to the attention of the regulators.